org.h2.index
Class BtreeIndex

java.lang.Object
  org.h2.engine.DbObjectBase
      org.h2.schema.SchemaObjectBase
          org.h2.index.BaseIndex
              org.h2.index.BtreeIndex

All Implemented Interfaces:

DbObject, Index, SchemaObject, RecordReader

public class BtreeIndex
extends BaseIndex
implements RecordReader

This is the most common type of index, a b-tree index. The index structure is:

• There is one BtreeHead that points to the root page. The head always stays where it is.
• There is a number of BtreePages. Each page is either a BtreeNode or a BtreeLeaf.
• A node page links to other leaf pages or to node pages. Leaf pages don't point to other pages (but may have a parent).
• The uppermost page is the root page. If pages are added or deleted, the root page may change.

Only the data of the indexed columns are stored in the index.

Field Summary

Fields inherited from class org.h2.index.BaseIndex

columnIds, columns, indexColumns, indexType, isMultiVersion, table

Fields inherited from class org.h2.engine.DbObjectBase

comment, database, trace

Fields inherited from interface org.h2.index.Index

EMPTY_HEAD

Fields inherited from interface org.h2.engine.DbObject

AGGREGATE, COMMENT, CONSTANT, CONSTRAINT, FUNCTION_ALIAS, INDEX, RIGHT, ROLE, SCHEMA, SEQUENCE, SETTING, TABLE_OR_VIEW, TRIGGER, USER, USER_DATATYPE

Constructor Summary

BtreeIndex(Session session, TableData table, int id, java.lang.String indexName, IndexColumn[] columns, IndexType indexType, int headPos)
Create a new b tree index with the given properties.

Method Summary

void	add(Session session, Row r) Add a row to this index.
boolean	canFindNext() Check if the index can get the next higher value.
boolean	canGetFirstOrLast() Check if this index can quickly find the first or last value.
void	checkRename() Check if this object can be renamed.
void	close(Session session) Close this index.
Cursor	find(Session session, SearchRow first, SearchRow last) Create a cursor to iterate over a number of rows.
Cursor	findFirstOrLast(Session session, boolean first) Find the first (or last) value of this index.
Cursor	findNext(Session session, SearchRow first, SearchRow last) Find a row or a list of rows that is larger and create a cursor to iterate over the result.
void	flush(Session session) Write all changed paged to disk and mark the index as valid.
double	getCost(Session session, int[] masks) Calculate the cost to find rows.
int	getHeadPos() Get the position of the head record.
long	getLastChange() Get the last change time or 0 if the index has not been changed.
long	getRowCount(Session session) Get the row count of this table, for the given session.
long	getRowCountApproximation() Get the approximated row count for this table.
boolean	needRebuild() Check if this index needs to be re-built.
Record	read(Session session, DataPage s) Read a record from the data page.
void	remove(Session session) Remove the index.
void	remove(Session session, Row row) Remove a row from the index.
void	truncate(Session session) Truncate the index.

Methods inherited from class org.h2.index.BaseIndex

commit, compareKeys, compareRows, containsNullAndAllowMultipleNull, getColumnIndex, getColumnListSQL, getColumns, getCostRangeIndex, getCreateSQL, getCreateSQLForCopy, getDropSQL, getDuplicateKeyException, getIndexColumns, getIndexType, getLookupCost, getPlanSQL, getRootPageId, getTable, getType, removeChildrenAndResources

Methods inherited from class org.h2.schema.SchemaObjectBase

getSchema, getSQL, initSchemaObjectBase

Methods inherited from class org.h2.engine.DbObjectBase

getChildren, getComment, getDatabase, getId, getModificationId, getName, initDbObjectBase, invalidate, isTemporary, rename, setComment, setModified, setObjectName, setTemporary, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.h2.schema.SchemaObject

getSchema

Methods inherited from interface org.h2.engine.DbObject

getChildren, getComment, getDatabase, getId, getModificationId, getName, getSQL, isTemporary, rename, setComment, setModified, setTemporary

Constructor Detail

BtreeIndex

public BtreeIndex(Session session,
                  TableData table,
                  int id,
                  java.lang.String indexName,
                  IndexColumn[] columns,
                  IndexType indexType,
                  int headPos)
           throws java.sql.SQLException

Create a new b tree index with the given properties. If the index does not yet exist, a new empty one is created.

Parameters:

session - the session

table - the base table

id - the object id

indexName - the name of the index

columns - the indexed columns

indexType - the index type

headPos - the position of the index header page, or Index.EMPTY_HEAD for a new index

Throws:

java.sql.SQLException

Method Detail

getHeadPos

public int getHeadPos()

Description copied from interface: DbObject

Get the position of the head record.

Specified by:

getHeadPos in interface DbObject

Overrides:

getHeadPos in class DbObjectBase

Returns:

the head position

remove

public void remove(Session session)
            throws java.sql.SQLException

Description copied from class: BaseIndex

Remove the index.

Specified by:

remove in interface Index

Specified by:

remove in class BaseIndex

Parameters:

session - the session

Throws:

java.sql.SQLException

flush

public void flush(Session session)
           throws java.sql.SQLException

Write all changed paged to disk and mark the index as valid.

Parameters:

session - the session

Throws:

java.sql.SQLException

close

public void close(Session session)
           throws java.sql.SQLException

Description copied from class: BaseIndex

Close this index.

Specified by:

close in interface Index

Specified by:

close in class BaseIndex

Parameters:

session - the session

Throws:

java.sql.SQLException

add

public void add(Session session,
                Row r)
         throws java.sql.SQLException

Description copied from class: BaseIndex

Add a row to this index.

Specified by:

add in interface Index

Specified by:

add in class BaseIndex

Parameters:

session - the session

r - the row to add

Throws:

java.sql.SQLException

remove

public void remove(Session session,
                   Row row)
            throws java.sql.SQLException

Description copied from class: BaseIndex

Remove a row from the index.

Specified by:

remove in interface Index

Specified by:

remove in class BaseIndex

Parameters:

session - the session

row - the row

Throws:

java.sql.SQLException

canFindNext

public boolean canFindNext()

Description copied from interface: Index

Check if the index can get the next higher value.

Specified by:

canFindNext in interface Index

Overrides:

canFindNext in class BaseIndex

Returns:

true if it can

findNext

public Cursor findNext(Session session,
                       SearchRow first,
                       SearchRow last)
                throws java.sql.SQLException

Description copied from class: BaseIndex

Find a row or a list of rows that is larger and create a cursor to iterate over the result. The base implementation doesn't support this feature.

Specified by:

findNext in interface Index

Overrides:

findNext in class BaseIndex

Parameters:

session - the session

first - the lower limit (excluding)

last - the last row, or null for no limit

Returns:

the cursor

Throws:

java.sql.SQLException

find

public Cursor find(Session session,
                   SearchRow first,
                   SearchRow last)
            throws java.sql.SQLException

Description copied from class: BaseIndex

Create a cursor to iterate over a number of rows.

Specified by:

find in interface Index

Specified by:

find in class BaseIndex

Parameters:

session - the session

first - the first row to return (null if no limit)

last - the last row to return (null if no limit)

Returns:

the cursor to iterate over the results

Throws:

java.sql.SQLException

getCost

public double getCost(Session session,
                      int[] masks)

Description copied from class: BaseIndex

Calculate the cost to find rows.

Specified by:

getCost in interface Index

Specified by:

getCost in class BaseIndex

Parameters:

session - the session

masks - the condition mask

Returns:

the cost

read

public Record read(Session session,
                   DataPage s)
            throws java.sql.SQLException

Description copied from interface: RecordReader

Read a record from the data page.

Specified by:

read in interface RecordReader

Parameters:

session - the session

s - the data page

Returns:

the record

Throws:

java.sql.SQLException

truncate

public void truncate(Session session)
              throws java.sql.SQLException

Description copied from class: BaseIndex

Truncate the index.

Specified by:

truncate in interface Index

Specified by:

truncate in class BaseIndex

Parameters:

session - the session

Throws:

java.sql.SQLException

checkRename

public void checkRename()

Description copied from class: DbObjectBase

Check if this object can be renamed. System objects may not be renamed.

Specified by:

checkRename in interface DbObject

Specified by:

checkRename in class DbObjectBase

needRebuild

public boolean needRebuild()

Description copied from class: BaseIndex

Check if this index needs to be re-built.

Specified by:

needRebuild in interface Index

Specified by:

needRebuild in class BaseIndex

Returns:

true if it must be re-built.

getLastChange

public long getLastChange()

Get the last change time or 0 if the index has not been changed.

Returns:

the last change time or 0

canGetFirstOrLast

public boolean canGetFirstOrLast()

Description copied from class: BaseIndex

Check if this index can quickly find the first or last value.

Specified by:

canGetFirstOrLast in interface Index

Specified by:

canGetFirstOrLast in class BaseIndex

Returns:

true if it can

findFirstOrLast

public Cursor findFirstOrLast(Session session,
                              boolean first)
                       throws java.sql.SQLException

Description copied from class: BaseIndex

Find the first (or last) value of this index. The cursor returned is positioned on the correct row, or on null if no row has been found.

Specified by:

findFirstOrLast in interface Index

Specified by:

findFirstOrLast in class BaseIndex

Parameters:

session - the session

first - true for the first value, false for the last

Returns:

a cursor (never null)

Throws:

java.sql.SQLException

getRowCount

public long getRowCount(Session session)

Description copied from interface: Index

Get the row count of this table, for the given session.

Specified by:

getRowCount in interface Index

Parameters:

session - the session

Returns:

the row count

getRowCountApproximation

public long getRowCountApproximation()

Description copied from interface: Index

Get the approximated row count for this table.

Specified by:

getRowCountApproximation in interface Index

Returns:

the approximated row count